Microwave furnace for continuous heat treating of various pieces of dielectric material

ABSTRACT

The furnace comprises a rectangular waveguide for a hyperfrequency wave generator and this waveguide is placed transversally to a tunnel furnace defining a longitudinal corridor, at least one part of said tunnel furnace being formed by two complementary half-shells assembled longitudinally to one another.

Uite States Patent Inventor Joel Henri Auguste Soulier 81 BoulevardMarceau, Colombes, France Appl. No. 874,341 Filed Nov. 5, 1969 PatentedJan. 4, 1972 Priority Dec. 5, 1968 France 176804 MICROWAVE FURNACE FORCONTINUOUS HEAT TREATING OF VARIOUS PIECES OF DIELECTRIC MATERIAL 9Claims, 7 Drawing Figs.

US. Cl 219/1055 Int. Cl 1105b 9/06 Field ofSearch 219/10.55

Primary Examiner-.1. V. Truhe Assistant Examinerl-lugh D. JaegerAttorney-Irving M. Weiner ABSTRACT: The furnace comprises a rectangularwaveguide for a hyperfrequency wave generator and this waveguide isplaced transversally to a tunnel furnace defining a longitudinalcorridor, at least one part of said tunnel furnace being formed by twocomplementary half-shells assembled longitudinally to one another.

PATENTEU JAN 4 B72 SHEET 1 UF 2 m FL Pic-11.5.

Pia-4 PATENTED JAN 4:972

SHEET 2 ,UF 2

Junnu MICROWAVE FURNACE FOR CONTINUOUS HEAT TREATING OF VARIOUS PIECESOF DIELECTRIC MATERIAL The present invention relates to a microwavefurnace, i.e., a furnace making use of hyperfrequency waves for treatingabsorbent dielectric materials, such as rubber and its derivatives.

The invention more particularly concerns a furnace enabling the heattreatment of strips or pieces of dielectric material of various sectionsproduced, for instance, at the exit of a slubbing machine.

Up till now, the heating of such pieces by means of microwaves has comeup against very great difficulties. Actually for enabling the heattreatment of a piece, such as a joint for a car body, it is necessary,on account of the speed at which slubbing machines work, to providerelatively long furnaces, or even a succession of several furnaces onebehind the other; an added problem in to make it possible to hold thepiece for treatment in a rigorous position in the cavity of the furnace.Also any dissipation towards the outside of hyperfrequency waves, whichmight be dangerous for workers, must be prevented.

Furthermore, the heat treatment undergone by the piece in the furnacehas the effect of giving off fumes and vapors, which deposit on theinner wall of the furnace. This has the effect, after a certain time, ofmaking the walls of the furnace absorbent, and consequently, greatlyaltering the characteristics of the work. This is compounded because afurnace of great length is obviously difficult to clean, or elsenecessitates taking down and rebuilding by experts who must be capableor again regulating the furnace.

The present invention completely solves the difficulties hitherto met increating a new microwave furnace.

According to the invention, the furnace comprises a rectangular waveguide for a hyperfrequency wave generator and this wave guide is placedtransversely to a tunnel furnace defining a longitudinal corridor, atleast part of the tunnel furnace being made of two complementaryhalf-shells assembled longitudinally to one another.

Various other characteristics of the invention will moreover be revealedby the detailed description which follows.

An embodiment of the invention is shown, by way of nonrestrictiveexample, in the accompanying drawings.

FIG. 1 is an elevation-section of the microwave furnace of theinvention.

FIG. 2 is a plane view seen from above partially cut away along the lineII-II of FIG. 1 of this furnace.

FIG. 3 is a section taken along the line III-III of FIG. 1.

FIG. 4 is a section taken along the line lV-IV of FIG. 1.

FIG. 5 is a section taken along the line VV of FIG. 1.

FIG. 6 is a section taken along the line VI-VI of FIG. 1.

FIG. 7 is a section taken along the line VII-VII of FIG. 1.

The furnace shown in the drawing for the continuous heat treatment ofdielectric materials, particularly rubber in the shape of pieces formedby a slubbing machine, is supported by a frame 1 which is made, forinstance, by means of tubes or other iron bars. Their particulararrangement has little importance with regard to the invention, becausethis frame has simply the function of supporting the assembly of membersof the furnace and means which are associated with it.

At its ends, the frame 1 is provided with sets of cheeks 2, 2a, of whichat least one set, in this case the set of checks 2 seen at the left partof FIG. 1, is provided with guiding slides 3 for the slides 4 supportinga spindle 5 on which a wheel 6 can revolve. Screws 7 are provided formoving the slides 4 so as to correlatively move the wheel 6 which fonnsa tightening wheel for an endless belt of a conveyor 8. This conveyor 8is also supported by a second wheel 60 mounted between the cheeks 2aandwhose shaft is associated with a driving device (not shown). Thus theconveyor 8 is continuously movable at a regular speed, but may beregulated necessary to hold the product for treatment as supported bythe conveyor 8 for a more or less long time in the furnace.

The furnace itself comprises a main body 9, comprising as shown inparticular in FIGS. 3 and 4, a sole-plate 10 from which asemicylindrical half-shell 11 is made, extended by longitudinal lateraledges 12, 12a.

At its end 9a the body 9 defines a cylindrical portion clearly shown inFIG. I, this portion fonning a clamp for fixing a waveguide 13 ofrectangular section. The body 9 supports a second semicylindricalhalf-shell 14, also having lateral and longitudinal edges 15, 15acomplementary to the edges 12, 12a and applied on the previous edges bymeans, on the one hand, of seal-tight washers I6, and on the other hand,of washer 17 of metal braid as shown in FIG. 4 for preventing anyoutward propagation towards the outside of hyperfrequency wavescirculating in the furnace, as explained in what follows.

Although it can be fixed in other ways, the half-shell I4 isadvantageously articulated on spindles 18 carried in supports 19 formedby the body 9, laterally in relation to the body as shown in FIGS. 2 and4. Articulated threaded rods 20 are provided on the other lateral sideof the body with tightening screws 21 bearing on the branches of flangesmade on the rim 15 of the half-shell 14.

FIG. 1 shows that the assembly of the body 9 and half-shell I4 defines atubular corridor 22 of circular section having the same diameter as thecylindrical part 9a of the end of said body 9.

A cylindrical passage or casing 23, of the same diameter as the corridor22, is fixed on the waveguide 13 in the extension of said corridor 22.This passage or casing 23 acts as housing for a piston 24 provided withsegments 25 of metal braid, the piston being able to slide in the nozzleor casing 23, which for this purpose, has slots 26 as shown in FIG. 2into which pass locking screws 27. The piston 24 is intended, when it ismoved, to enable the tuning of the wavelength in the guide 13 and thedistribution of the calorific power developed in the vicinity of theintersection of the waveguide and corridor 22 of the fumace, at the sametime permitting adaption of the magnetron which is the microwavesgenerator, said magnetron being mounted on the waveguide by an end piece28.

For tuning the wavelength in the furnace the waveguide 13 is provided asshown in FIGS. 1 and 7 with a resonator 29 placed at the top part ofsaid waveguide and supported by a core 30. The care 30 is movableaxially, under the guidance of gudgeons 31 by means of a screw 32 whichis in turn controlled by a milled knob 33. This knob 33 is placed in aslot 34 defined inside a cover 35 closing the top part of the waveguide13. The resonator 29 is, as shown in FIG. 7, formed by a kind of metalcase reflecting the hyperfrequency waves.

The tunnel-furnace unit described above and formed by the body 9, thehalf-shell 14 forming a cover, the waveguide 13 and the passage orcasing 23, is supported, as shown in FIGS. I and 6, so as to be able tobe adjusted for height. To this end, a plate 36 is provided which isdirectly carried by the frame I and which, at both ends, supports jacksdesignated on the whole by 37 and 38 in FIG. 1, of which jacks anembodiment is shown in FIG. 6. These jacks comprise a tubular cover 39fonning wings 40 by which said cover is connected to the plate 36 bymeans of crossbars 41. The cover 39 contains a bearing 42 inside for apin 43 whose cut end 434 penetrates into the sole-piece 10 of the body 9of the furnace. A bearing flange 44 made integral with the pin 43 isfixed on the body 9 by a screw 45 so as to prevent any rotation of thepin 43 which has a threaded portion 42a underneath its part arranged inthe bearing 42, on a portion which a tapped chain wheel 46 is screwed.The chain wheel 46 is securely held between the bearing 42 and cover 47fixed on the underneath of the cover 39, said cover 47 being tranversedby a threaded stem 43b of the pin 43, on which a lock nut 48 is fixed.

As shown in FIG. 1, the chain wheels 46 of the two jacks 37 and 38 areheld together by a chain 49 constantly tightened by a spring 50, thischain comprising an operating handle 51 forming a pointer 51a moving infront of graduations carried by a scale 52 fixed on the frame 1.

From the foregoing, one sees that by moving the handle 51, the chainwheels 46 are revolved of the two jacks whose threading axially drives,in a rising or descending direction,

the pins 43 of said two jacks, and then, the furnace unit describedabove, is correlatively raised or lowered.

The plate 36, supporting the jacks described above, also supportspistons 53 clearly visible in FIG. 3, which are provided with braidedmetal washers 54 and sealtight washers $5 for bearing in cylindricalhousings provided in the sole-piece of the body 9 so that said pistonsproject inside the corridor or cavity 22 of the furnace. The pistons 53are extended by forks 56 acting as support and guide for the conveyor 8formed by a cloth of material permeable to hyperfrequency waves, forinstance, glass fabric coated with silicon- The guiding forks 56 of thecloth being relatively close to each other, one is assured that thiscloth does not sag in any manner inside the furnace cavity, whichenables one to make certain that the heat-treated object, the rubberpiece 57, for instance, shown in FlZGS. 3 and 4, is always properlymaintained in the axis of the furnace, so that it is uniformly treated.

According to the particular shape assumed by the piece 57 for treatmentand also according to its cross section dimension, it is obviouslynecessary to regulate the position of the conveyor 8 in relation to thelongitudinal axis of the tunnel or cavity 22, which is done as explainedin the foregoing, by causing the furnace to rise or descend, whoseposition is repeated in relation to that of the conveyor, which is fixedfor height, by means of the pointer 51a of the operating handle 51.

So that the hyperfrequency waves produced in the furnace cavity cannotpropagate outside the cavity, there is provided in the tuning piston 24containing the passage or casing 23, an opening 24a whose cross sectionshape is as close as possible to that of the piece for treatment.Furthermore, this piston is advantageoulsy made of material absorbinghyperfrequency waves, carbon for instance, and in like manner, theopposite end of the cavity 22 is provided with a plug 58, preferably ofcarbon, which is provided with a sealtight washer 59 and a metal braidwasher 60. This plug is obviously hollow to enable the passage of theconveyor 8 and piece 57 and is provided on its part projecting beyondthe cavity 22 with a perforated cover 61 for holding a movable register62 acting both for guiding the conveyor 8 and closing said plug 58 ascompletely as possible.

In addition to the members described in the foregoing, the furnacecomprises, inside the tunnel or cavity 22, annular rings 63 which areplaced in the part of half-shell cavity 22 defined by the body 9 andhalf-shell 14. These annular rings, which are quite thin, for instance,5 to 6/10ths of a millimeters have a width depending on the wavelengthproduced by the magnetron. Additionally they are separated from eachother, as shown in FIG. 1, by a distance d corresponding to half thewavelengths produced, so the electric field set up in the furnace cavitytends to close, as shown at 64 in FIG. 1 around the successive rings.Thus the magnetic field shown by dots is contained inside the volumedefined by each ring.

One sees in FIG. 4 that inside of the rings the electric field 64 isthus developed radially from the axis of the cavity 22, whereas themagnetic field, designated by 65 remains annular and concentric to saidrings inside said rings.

Supplementarily, one provides level with the waveguide 13, a sleeve 66of material permeable to hyperfrequency waves, for instance, oftetrafluoroethylene, this sleeve being keyed at the mounting, so thatthe magnetic field properly closes inside the copper rings 63. Thesleeve 66 also has the function of preventing smoke or vapors comingwith the heating of the piece 57 from penetrating into the waveguide 13.By making the sleeve 66 more or less slide, the position of the wavephase is actually regulated.

As can be seen from the foregoing, the various constitutive parts of thefurnace, namely, principally the body 9 and halfshell 14 forming itscover, likewise the passage or casing 23 as well as the wave guide 13,are made of material reflecting hyperfrequency waves, and for instance,of light alloy, so that these parts can easily be made by moulding andmachining. Since the half-shell 14 acting as a cover is easily removed,and since the rings 63 in which the magnetic field is enclosed arespaced apart in relation to each other it is possible to clean theinside of the furnace without any taking down. Moreover, the piston 24and likewise the plug 58 can also be made, although this is not shown inthe drawings, of two complementary halfshells, so that these parts, can,if so desired, be changed when it is necessary to treat a piece ofanother shape, this change thus being carried out without needing totake the conveyor 8 down.

The invention is not restricted to the embodiment shown and described indetail, for other modifications can be applied to it without goingoutside its scope.

I claim:

1. Microwave furnace for the continuous heat treatment of various piecesof dielectric materials comprising:

a hyperfrequency wave generator,

a tunnel furnace defining a longitudinal corridor, one part of saidtunnel furnace being made by two complementary half-shells assembledlongitudinally to each other,

a waveguide connected to said generator and transversely to the tunnelfurnace whereby hyperfrequency waves are transmitted along said tunnelfurnace, and

a sleeve inserted in the tunnel furnace, at its junction with therectangular guide, this sleeve being made of material penneable tohyperfrequency waves and being mounted for being axially regulated foradjusting the wave phase in the waveguide and preventing the propagatingof smoke and vapors in the waveguide.

2. Microwave furnace for the continuous heat treatment of various piecesof dielectric materials comprising:

a hyperfrequency wave generator,

tunnel furnace defining a longitudinal corridor, one part of said tunnelfurnace being made by two complementary half-shells assembledlongitudinally to each other,

a waveguide connected to said generator and transversely to the tunnelfurnace whereby hyperfrequency waves are transmitted along said tunnelfurnace,

said tunnel furnace containing continuous walled rings and a belt of anendless conveyor, and

supports within said tunnel furnace and projecting between said ringsfor guiding the belt of said endless conveyor, said supports projectingfrom pistons traversing the wall of the tunnel furnace, said pistonsbeing joined together and means being provided for regulating the mutualposition of the tunnel furnace in relation to the pistons, so that theposition of the conveyor belt is adjustable inside said tunnel furnace.

3. Microwave furnace as claimed in claim 2 in which the pistons arerigidly fixed on a plate which is carried by a frame and the tunnelfurnace assembly is connected to said frame by means of at least onejack, so that the regulating of the position of the conveyor belt inrelation to said tunnel furnace is done by moving said tunnel furnace.

4. Microwave fumace for the continuous heat treatment of various piecesof dielectric materials comprising:

a hyperfrequency wave generator,

a tunnel fumace defining a longitudinal corridor, one part of saidtunnel furnace being made by two complementary half-shells assembledlongitudinally to each other,

a waveguide connected to said generator and transversely to the tunnelfurnace whereby hyperfrequency waves are transmitted along said tunnelfurnace, and

braided metal washers between each of the tunnel furnace parts forpreventing the propagation towards the exterior of the electric fieldproduced in the tunnel furnace.

5. Microwave furnace for the continuous heat treatment of various piecesof dielectric materials, comprising:

a hyperfrequency wave generator;

a tunnel fumace defining a longitudinal corridor;

one part of said tunnel furnace being made by two complementaryhalf-shells removably assembled longitudinally together along twolongitudinal joints;

a waveguide connected to said generator and transversally to said tunnelfurnace whereby hyperfrequency waves are transmitted along said tunnelfurnace;

said tunnel furnace further containing at least in its part formed bysaid two complementary half-shells, continuous walled conducting ringswhich are spaced apart by a distance substantially equal to ahalf-wavelength of the hyperfrequency waves developed in the volume ofsaid tunnel furnace by said generator whereby electric fields which aregenerated may close inside said rings despite joints between saidcomplementary half-shells.

6. Microwave furnace as claimed in claim 5 in which:

said tunnel furnace contains a belt of an endless belt conveyor forholding a piece of dielective material to be heattreated;

said conveyor is made of a material permeable to hyperfrequency waves,particularly of glass fabric coated with silicon;

and said belt is carried inside said tunnel furnace by adjustablesupports located to project between said continuous walled conductingrings.

7. Microwave furnace characterized substantially in ac cordance withclaim 5, wherein a sleeve is inserted in said tunnel furnace at itsjunction with said waveguide, said sleeve being made of a material whichis permeable to hyperfrequency waves and which is mounted for beingaxially regulated for adjusting the wave phase in said waveguide andpreventing the propagating of smoke and vapors in said waveguide.

8. Microwave furnace characterized substantially in accordance withclaim 6, wherein said supports for said belt project from pistonstraversing the wall of said tunnel furnace, said pistons being joinedtogether and means being provided for regulating the mutual position ofsaid tunnel furnace in relation to said pistons so that the position ofsaid belt is adjustable inside said tunnel furnace.

9. Microwave furnace characterized substantially in accordance withclaim 8, wherein said pistons are rigidly fixed on a plate which iscarried by a frame, and said tunnel furnace assembly is connected tosaid frame by means of at least one jack so that the regulating of theposition of the belt in relation to said tunnel furnace is accomplishedby moving said tunnel furnace.

1. Microwave furnace for the continuous heat treatment of various piecesof dielectric materials comprising: a hyperfrequency wave generator, atunnel furnace defining a longitudinal corridor, one part of said tunnelfurnace being made by two complementary half-shells assembledlongitudinally to each other, a waveguide connected to said generatorand transversely to the tunnel furnace whereby hyperfrequency waves aretransmitted along said tunnel furnace, and a sleeve inserted in thetunnel furnace, at its junction with the rectangular guide, this sleevebeing made of material permeable to hyperfrequency waves and beingmounted for being axially regulated for adjusting the wave phase in thewaveguide and preventing the propagating of smoke and vapors in thewaveguide.
 2. Microwave furnace for the continuous heat treatment ofvarious pieces of dielectric materials comprising: a hyperfrequency wavegenerator, a tunnel furnace defining a longitudinal corridor, one partof said tunnel furnace being made by two complementary half-shellsassembled longitudinally to each other, a waveguide connected to saidgenerator and transversely to the tunnel furnace whereby hyperfrequencywaves are transmitted along said tunnel furnace, said tunnel furnacecontaining continuous walled rings and a belt of an endless conveyor,and supports within said tunnel furnace and projecting between saidrings for guiding the belt of said endless conveyor, said supportsprojecting from pistons traversing the wall of the tunnel furnace, sAidpistons being joined together and means being provided for regulatingthe mutual position of the tunnel furnace in relation to the pistons, sothat the position of the conveyor belt is adjustable inside said tunnelfurnace.
 3. Microwave furnace as claimed in claim 2 in which the pistonsare rigidly fixed on a plate which is carried by a frame and the tunnelfurnace assembly is connected to said frame by means of at least onejack, so that the regulating of the position of the conveyor belt inrelation to said tunnel furnace is done by moving said tunnel furnace.4. Microwave furnace for the continuous heat treatment of various piecesof dielectric materials comprising: a hyperfrequency wave generator, atunnel furnace defining a longitudinal corridor, one part of said tunnelfurnace being made by two complementary half-shells assembledlongitudinally to each other, a waveguide connected to said generatorand transversely to the tunnel furnace whereby hyperfrequency waves aretransmitted along said tunnel furnace, and braided metal washers betweeneach of the tunnel furnace parts for preventing the propagation towardsthe exterior of the electric field produced in the tunnel furnace. 5.Microwave furnace for the continuous heat treatment of various pieces ofdielectric materials, comprising: a hyperfrequency wave generator; atunnel furnace defining a longitudinal corridor; one part of said tunnelfurnace being made by two complementary half-shells removably assembledlongitudinally together along two longitudinal joints; a waveguideconnected to said generator and transversally to said tunnel furnacewhereby hyperfrequency waves are transmitted along said tunnel furnace;said tunnel furnace further containing at least in its part formed bysaid two complementary half-shells, continuous walled conducting ringswhich are spaced apart by a distance substantially equal to ahalf-wavelength of the hyperfrequency waves developed in the volume ofsaid tunnel furnace by said generator whereby electric fields which aregenerated may close inside said rings despite joints between saidcomplementary half-shells.
 6. Microwave furnace as claimed in claim 5 inwhich: said tunnel furnace contains a belt of an endless belt conveyorfor holding a piece of dielective material to be heat-treated; saidconveyor is made of a material permeable to hyperfrequency waves,particularly of glass fabric coated with silicon; and said belt iscarried inside said tunnel furnace by adjustable supports located toproject between said continuous walled conducting rings.
 7. Microwavefurnace characterized substantially in accordance with claim 5, whereina sleeve is inserted in said tunnel furnace at its junction with saidwaveguide, said sleeve being made of a material which is permeable tohyperfrequency waves and which is mounted for being axially regulatedfor adjusting the wave phase in said waveguide and preventing thepropagating of smoke and vapors in said waveguide.
 8. Microwave furnacecharacterized substantially in accordance with claim 6, wherein saidsupports for said belt project from pistons traversing the wall of saidtunnel furnace, said pistons being joined together and means beingprovided for regulating the mutual position of said tunnel furnace inrelation to said pistons so that the position of said belt is adjustableinside said tunnel furnace.
 9. Microwave furnace characterizedsubstantially in accordance with claim 8, wherein said pistons arerigidly fixed on a plate which is carried by a frame, and said tunnelfurnace assembly is connected to said frame by means of at least onejack so that the regulating of the position of the belt in relation tosaid tunnel furnace is accomplished by moving said tunnel furnace.